Fluoroelastomer compositions

ABSTRACT

Fluoropolymers comprising a fluoroelastomer matrix incorporating therein particles of a semicrystalline fluoropolymer formed of tetrafluoroethylene (TFE) homopolymers or copolymers, wherein the average particle sizes of the semicrystalline fluoropolymer latex range from 10 to 100 nm.

This application is a continuation of U.S. patent application Ser. No.10/843,440 filed on May 12, 2004, which is a continuation of U.S.application Ser. No. 10/118,066, filed on Apr. 4, 2002, which is acontinuation of U.S. application Ser. No. 09/511,949 filed on Feb. 23,2000, all of which are incorporated by reference herein.

The present invention relates to fluoropolymers essentially formed by amixture of a fluoroelastomer and a semicrystalline fluoropolymer usablefor sealing manufactured articles in the electronic, optical andpharmaceutical industry.

More specifically the present invention relates to fluoropolymers formedby a mixture of a fluoroelastomer and a semicrystalline fluoropolymer,characterized by improved mechanical properties combined with goodproperties of elastic retention (lower compression set) and very goodsurface appearance without roughness. It is well known that one of thefluoroelastomer uses is the preparation of O-rings for seals: for thisapplication it is essential that the O-ring surface is smooth.

The use of fluoroelastomers containing polytetrafluoroethylene (PTFE)particles to improve the properties of abrasion-resistance and of hottearing the obtained manufactured articles is known in the prior art. Asdescribed in Japanese patent 57-107,336, the fluoroelastomerabrasion-resistance is improved by physically mixing solid curablefluoroelastomers with PTFE powders having a low molecular weight, in therange 500-200,000 as average molecular weight by number (M_(n)). SaidPTFE is prepared by thermal decomposition at a temperature between 450°C. and 600° C. for prolonged times or by irradiation with ionicradiation of high molecular weight PTFE. An alternative method forobtaining PTFE having a low molecular weight is that to polymerize TFEin the presence of chain transfer agents. The fluoroelastomer and thePTFE powders are mixed in Banbury or in calender.

In U.S. Pat. No. 4,879,362 and U.S. Pat. No. 4,904,726 mixtures offluoroelastomers with resins of PTFE modified with the addition ofcomonomers such as hexafluoropropene (HFP), perfluoropropylvinylether(PPVE), etc., are used, in order to avoid PTFE fibrillation problemswithout losing the reinforcement properties that the PTFE gives to theobtained fluoroelastomers. The comonomer results much more present onthe polymeric particle surface, so as to allow an uniform distributionin the fluoroelastomer without the formation of visible agglomerates.The latter should be the cause of fibrillation phenomena.

In EP 708,797 fluoroelastomer compositions formed by a fluoroelastomerand by a semicrystalline fluorinated filler in the form of micropowderwhich are obtained in curing compounds not containing metal species, aredescribed. Said compositions give a low release of metal species underconditions where an high purity is required, but they show poormechanical properties. Tests carried out by the Applicant (see thecomparative Examples), have shown that the surface of the manufacturedarticles obtained from said fluoroelastomer compositions showsroughness. It is well known that in the O-ring preparation, typicalfluoroelastomer application, surfaces having a low roughness in order toobtain good sealing properties, are required. The semicrystallinefluorinated filler is based on PTFE or PTFE modified with a comonomerand obtained by emulsion or suspension polymerization. The highmolecular weight PTFE is subjected to irradiation, as above said, inorder to reduce the molecular weight. This makes easier the PTFE millingproduced by a suspension process; it eliminates the fibrillation andreduces the PTFE agglomeration obtained by an emulsion process.

The need was felt to have available fluoroelastomer compositionscomprising a semicrystalline fluorinated filler having improvedproperties compared with those of the prior art and specifically withthe following property combination:

-   -   improved mechanical properties    -   good elastic retention properties (lower compression set-very        good seal)    -   very good surface appearance roughness free.

The Applicant has unexpectedly and surprisingly found that it ispossible to obtain the combination of the above mentioned properties, byincorporating in the fluoroelastomer matrix PTFE particles or itscopolymers having well defined sizes as specified hereinafter.

It is therefore an object of the present invention fluoropolymerscomprising a fluoroelastomer matrix incorporating therein particles of asemicrystalline fluoropolymer latex formed by tetrafluoroethylene (TFE)homopolymers, or TFE copolymers with one or more monomers containing atleast one ethylene unsaturation in amounts ranging from 0.01% to 10% bymoles, preferably from 0.05% to 5% by moles, wherein the averageparticle sizes of the semicrystalline fluoropolymer latex range from 10to 100 nm, preferably from 10 to 60 nm. Also semycrystallinefluoropolymers wherein the latex particle sizes have the above mentionedvalue for at least 60% by weight, preferably 70% by weight of thesemicrystalline fluoropolymer, can be used.

The invention compositions are obtainable by mixing the semicrystallinefluoropolymer latex with the fluoroelastomer latex and subsequentcoagulation. Alternatively the invention compositions can be polymerizedin the same reactor in two subsequent steps: in a first step thesemicrystalline fluoropolymer with the mentioned nanometric sizes ispolymerized and in a second step the fluoroelastomer is polymerized. Byoperating in this way the fluoroelastomer should cover thesemicrystalline fluoropolymer latex particles, allowing to obtain a verygood dispersion of the latter in the fluoroelastomer.

The semicrystalline fluoropolymer amount inside the fluoroelastomermatrix is in the range 2%-40% by weight, preferably 5-30% by weight,more preferably 10-20% by weight on the total of the polymeric mixture.

The semicrystalline fluoropolymer particles having the above mentionedsizes are obtainable for example by a polymerization process in anaqueous microemulsion of perfluoropolyoxyalkylenes as described forexample in the European patent application EP 99112083.3 in the name ofthe Applicant, herein incorporated by reference. Microemulsionpolymerization methods can also be used, wherein the oil phase is formedby polymerizable unsaturated monomers, as described in U.S. Pat. No.5,523,346 and in U.S. Pat. No. 5,616,648.

The fluoroelastomers can be prepared by copolymerization of the monomersin aqueous emulsion, according to well known methods in the prior art,in the presence of radical initiators (for example alkaline or ammoniumpersulphates, perphosphates, perborates, percarbonates), optionally incombination with ferrous, cuprous or silver salts, or of other easilyoxidizable metals. In the reaction medium also surfactants of variouskind, among which the fluorinated surfactants are particularlypreferrred, are usually present.

Alternatively the fluoroelastomers can be prepared in bulk or insuspension, in an organic liquid in which a suitable radical initiatoris present, according to well known techniques.

The polymerization reaction is generally carried out at temperatures inthe range 25°-150° C., under a pressure up to 10 MPa.

The fluoroelastomers are preferably prepared in microemulsion ofperfluoropolyoxyalkylens, according to U.S. Pat. No. 4,789,717 and U.S.Pat. No. 4,864,006.

The Applicant has found that in order to obtain the results of thepresent invention it is essential that the semi-crystallinefluoropolymer filler latex has the mentioned nanometric sizes, while thesize of the latex of the fluoroelastomer is not critical.

When the semi-crystalline fluorinated filler is based on modified PTFE,for its preparation comonomers having an ethylene unsaturation both ofhydrogenated and fluorinated type, can be used. Among thosehydrogenated, ethylene, propylene, acrylic monomers, for examplemethylmethacrylate, (meth)acrylic acid, butylacrylate,hydroxyethylhexyl-acrylate, styrene monomers can be mentioned.

Among the fluorinated comonomers we can mention:

-   -   perfluoroolefins C₃-C₈, such as hexafluoropropene (HFP),        hexafluoroisobutene;    -   hydrogenated fluorolefins C₂-C₈, such as vinyl fluoride (VF),        vinylidene fluoride (VDF), trifluoroethylene,        perfluoroalkylethylene CH₂═CH—R_(f), wherein R_(f) is a        perfluoroalkyl C₁-C₆;    -   chloro- and/or bromo- and/or iodo-fluoroolefins C₂-C₈, such as        chlorotrifluoroethylene (CTFE);    -   (per)fluoroalkylvinylethers (PAVE) CF₂═CFOR_(f), wherein R_(f)        is a (per)fluoroalkyl C₁-C₆, for example CF₃, C₂F₅, C₃F₇;    -   (per)fluoro-oxyalkylvinylethers CF₂═CFOX, wherein X is: an alkyl        C₁-C₁₂, or an oxyalkyl C₁-C₁₂, or a (per)fluorooxyalkyl C₁-C₁₂        having one or more ether groups, for example        perfluoro-2-propoxy-propyl; fluorodioxoles, preferably        perfluorodioxoles.

PAVEs are preferred comonomers, specifically perfluoromethyl-, ethyl-,propylvinylether and fluorodioxoles, preferably perfluorodioxoles.

The fluoroelastomers used in the present invention belong to thefollowing classes:

-   (1) VDF-based copolymers, wherein VDF is copolymerized with at least    one comonomer selected from the following: perfluoroolefins C₂-C₈,    such as tetrafluoroethylene (TFE) hexafluoropropene (HFP); chloro-    and/or bromo- and/or iodo-fluoroolefins C₂-C₈, such as    chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene;    (per)fluoroalkylvinylethers (PAVE) CF₂═CFOR_(f), wherein R_(f) is a    (per)-fluoroalkyl C₁-C₆, for example trifluoromethyl,    bromodifluoromethyl, pentafluoropropyl; perfluorooxyalkylvinylethers    CF₂═CFOX, wherein X is a perfluorooxyalkyl C₁-C₁₂ having one or more    ether groups, for example perfluoro-2-propoxy-propyl; non    fluorinated olefins (Ol) C₂-C₈, for example ethylene and propylene;-   (2) TFE-based copolymers, wherein TFE is copolymerized with at least    one comonomer selected from the following:    (per)fluoroalkylvinylethers (PAVE) CF₂═CFOR_(f), wherein R_(f) is as    above defined; perfluoro-oxyalkylvinylethers CF₂═CFOX, wherein X is    as above defined; fluoroolefins C₂-C₈ containing hydrogen and/or    chloro and/or bromo and/or iodo atoms; non fluorinated olefins (Ol)⁻    C₂-C₈; perfluorovinylethers containing hydrocyanic groups as    described in U.S. Pat. No. 4,281,092, U.S. Pat. No. 5,447,993, U.S.    Pat. No. 5,789,489.

Preferably the invention fluoroelastomers contain perfluorinatedmonomers, and preferably the base structure of these fluoroelastomers isselected from the copolymers of class (2), wherein TFE is polymerizedwith one or more perfluorinated comonomers as above mentioned.

Within the above defined classes, preferred compositions by moles of themonomers forming the base structure of the fluoroelastomer are thefollowing:

-   -   (a) vinylidene fluoride (VDF) 45-85%, hexa-fluoropropene (HFP)        15-45%, tetrafluoroethylene (TFE) 0-30%;    -   (b) vinylidene-fluoride (VDF) 50-80%, perfluoroalkylvinylether        (PAVE) 5-50%, tetrafluoroethylene (TFE) 0-20%;    -   (c) vinylidene fluoride (VDF) 20-30%, non fluorinated olefins        (Ol) C₂-C₈ 10-30%, hexafluoropropene (HFP) and/or        perfluoroalkylvinylether (PAVE) 18-27%, tetrafluoroethylene        (TFE) 10-30%;    -   (d) tetrafluoroethylene (TFE) 50-80%, perfluoroalkylvinylether        (PAVE) 20-50%;    -   (e) tetrafluoroethylene (TFE) 45-65%, non fluorinated olefins        (Ol) C₂-C₈ 20-55%, vinylidene fluoride 0-30%;    -   (f) tetrafluoroethylene (TFE) 32-60% by moles, non fluorinated        olefins (Ol) C₂-C₈ 10-40%, perfluoroalkylvinylether (PAVE)        20-40%;    -   (g) tetrafluoroethylene (TFE) 33-75%, perfluoroalkylvinylether        (PAVE) 15-45%, vinylidene fluoride (VDF) 5-30%.

Specific particularly preferred compositions are:

-   -   (d) TFE 50-80%, PAVE 20-50%;    -   (g) TFE 33-75%, PAVE 15-45%, VDF 5-30%.

Optionally the fluoroelastomers comprise also monomer units derivingfrom a bis-olefin having general formula:

wherein:R₁, R₂, R₃, R₄, R₅, R₆, equal to or different from each other, are H oralkyls C₁-C₅;Z is a linear or branched, alkylene or cycloalkylene C₁-C₁₈ radical,optionally containing oxygen atoms, preferably at least partiallyfluorinated, or a (per)fluoropolyoxyalkylene radical, as described in EP661,304 in the name of the Applicant.

The unit amount in the chain deriving from said bis-olefins is generallyin the range 0.01-1.0 by moles, preferably 0.03-0.5 by moles, still morepreferably 0.05-0.2% by moles for 100 moles of the other above mentionedmonomer units forming the fluoroelastomer base structure.

The fluoropolymers of the present invention can be cured by peroxidicroute, wherefore they preferably contain along the chain and/or interminal position of the macromolecules iodine and/or bromine atoms. Theintroduction of such iodine and/or bromine atoms can be achieved byaddition, in the reaction mixture, of brominated and/or iodinatedcure-site comonomers, such as bromo and/or iodo olefins having from 2 to10 carbon atoms (as described for example in U.S. Pat. No. 4,035,565 andU.S. Pat. No. 4,694,045), or iodo and/or bromo fluoroalkylvinylethers(as described in U.S. Pat. No. 4,745,165, U.S. Pat. No. 4,564,662 and EP199,138), in such amounts so that the content of cure-site comonomers inthe final product is generally in the range 0.05-2 moles for 100 molesof the other base monomer units.

Other usable iodinated compounds are the triodinated deriving fromtriazines as described in European patent application EP 860,436 and inthe European patent application EP 99114823.0.

Alternatively or also in association with the cure-site comonomers it ispossible to introduce iodine and/or bromine end atoms by addition to thereaction mixture of iodinated and/or brominated chain transfer agents,such as for example the compounds of formula R_(f)(I)_(x)(Br)_(y),wherein R_(f) is a (per)fluoroalkyl or a (per)fluorochloroalkyl havingfrom 1 to 8 carbon atoms, while x and y are integers between 0 and 2,with 1≦x+y≦2 (see for example U.S. Pat. No. 4,243,770 and U.S. Pat. No.4,943,622). It is also possible to use, as chain transfer agents,alkaline or earth-alkaline metal iodides and/or bromides, according toU.S. Pat. No. 5,173,553.

In association with the chain transfer agents containing iodine and/orbromine, other chain transfer agents known in the prior art, such asethyl acetate, diethylmalonate, etc., can be used.

Curing by peroxidic route is carried out, according to known techniques,by addition of a suitable peroxide capable to generate radicals bythermal decomposition. Among the most commonly used we mention:dialkylperoxides, such as for example di-terbutyl-peroxide and2,5-dimethyl-2,5-di-(terbutylperoxy)hexane; dicumyl peroxide; dibenzoylperoxide; diterbutyl perbenzoate; di[1,3-dimethyl-3-(terbutylperoxy)-butyl]carbonate. Other peroxidicsystems are described, for example, in European patent applications EP136,596 and EP 410,351.

To the compound (curable blend) other products are then added, such as:

-   (a) curing coagents, in an amount generally in the range 0.5-10%,    preferably 1-7% by weight with respect to the polyymer; among them,    triallyl-cyanurate; triallyl-isocyanurate (TAIC);    tris(diallylamine)-s-triazine; triallylphosphite;    N,N-diallyl-acrylamide; N,N,N′,N′-tetraallylmalonamide;    trivinyl-isoyanurate; 2,4,6-trivinyl-methyltrisiloxane, etc., are    commonly used; TAIC is particularly preferred; other preferred    crosslinking agents are bis-olefins described in the European patent    application EP 769,520. Other crosslinking agents which can be used    are the triazines described in the European patent applications EP    860,436 and WO97/05122.-   (b) optionally a metal compound, in an amount in the range 1-15%,    preferably 2-10%, by weight with respect to the polymer, selected    from oxides or hydroxides of divalent metals, such as for example,    Mg, Zn, Ca or Pb, optionally associated to a weak acid salt, such as    for example stearates, benzoates, carbonates, oxalates or phosphites    of Ba, Na, K, Pb, Ca;-   (c) optionally acid acceptors of the non metal oxide type, such as    1,8 bis dimethyl amino naphthalene, octadecylamine etc. as described    in EP 708,797.-   (d) other conventional additives, such as thickening fillers,    pigments, antioxidants, stabilizers and the like.

When the fluoroelastomer matrix contains cyano groups, the fluoropolymercuring of the present invention is carried Out by using as crosslinkingagents tin organic compounds or di-aromatic aminic compounds, asdescribed in U.S. Pat. No. 4,394,489, U.S. Pat. No. 5,767,204, U.S. Pat.No. 5,789,509. This type of curing can be associated to a curing ofperoxidic type, when the fluoroelastomer matrix contains iodine orbromine atoms, preferably end atoms, as described in U.S. Pat. No.5,447,993.

The present invention will be better illustrated by the followingExamples, which have a merely indicative but not limitative purpose ofthe scope of the invention itself.

EXAMPLE 1

a) Preparation of the Semicrystalline Fluoropolymer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 272 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   59 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   59 ml of a 30% by volume NH₄OH aqueous solution;    -   118 ml of demineralized water;    -   36 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. 0.48 bar of C₂H₆ were fedinto the autoclave and the pressure was increased and maintainedconstant at 11 bar during the whole polymerization with TFE.

6.5 g of ammonium persulphate (APS) as initiator agent were thenintroduced into the autoclave. After 37 minutes of reaction, theautoclave was cooled and the latex discharged. The latex characteristicsare reported in Table 1.

b) Preparation of the Fluoroelastomer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 67 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   14.5 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   14.5 ml of a 30% by volume NH₄OH aqueous solution;    -   29 ml of demineralized water;    -   9 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(m)(CF₂O)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The following mixture ofmonomers was then fed: perfluoromethylvinylether (PMVE) 60% by molestetrafluoroethylene (TFE) 40% by molesso as to increase the pressure to 25 bar.

-   -   0.32 g of ammonium persulphate (APS) as initiator agent;    -   26 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   5 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the addition        was carried out in 20 portions, each of 0.25 g, starting from        the polymerization beginning and for every increase in the        monomer conversion,    -   were then introduced in the autclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 137 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex properties are reported in Table 1.

c) Mixing of the Latexes Preparation of the Final Polymer

635.6 ml of the latex obtained in Example 1a are mixed with 1517 ml ofthe Example 1b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for every litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 2, were obtained.

EXAMPLE 2 (COMPARATIVE)

a) Preparation of the Semicrystalline Fluoropolymer

In a 50 l autoclave, equipped with a stirrer working at 245 rpm, 32 l ofdemineralized water, 12 g of ammonium prfluorooctanoate and 140 g ofparaffin with melting point 52-56° C. were introduced, after evacuation.

The autoclave was then heated to 89° C. and progressively increased upto 102.1° C. with a rate of 1° C. per minute for the whole reactionduration. 350 mbar of ethane were fed into the autoclave and thepressure was increased and maintained at 20 bar by continuously feedingTFE during the polymerization.

3.5 g of ammonium prsulphate (APS) as initiator agent and subsequentlyfurther 2 g of an APS aqueous solution at a flow-rate of 50 cc/min wereintroduced in the autoclave.

After 73 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex characteristics are reported in Table 1.

b) Preparation of the Fluoroelastomer

The fluoroelastomer latex was obtained as described in Example 1b.

c) Mixing of the Latexes—Preparation of the Final Polymer

428.5 ml of the latex obtained in Example 2a are mixed with 1517 ml ofthe Example 2b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for every litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 2, were obtained.

EXAMPLE 3 (COMPARATIVE)

a) Preparation of the Semicrystalline Fluoropolymer

The PTFE latex was obtained in the presence of a microemulsion as inExample 1a. The latex was subsequently coagulated with an aluminumsulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex) and driedat 150° C. in an air-circulation oven for 24 hours.

b) Preparation of the Fluoroelastomer

The perfluoroelastomer latex was obtained as described in Example 1b.The latex was subsequently coagulated with an aluminum sulphate solution(6 g of Al₂(SO₄)₃ for each litre of latex) and dried at 100° C. in anair-circulation oven for 12 hours.

c) Mechanical Mixing—Preparation of the Final Polymer

425 g of fluoroelastomer of Example 3b were mixed with 75 g of PTFEpowder obtained from Example 3a in an open mixer with rollers heated at60° C. In the mixing process the perfluoroelastomer is introduced firstwith the rollers completely near the one to the other and mixed until acontinuous polymer film is obtained. The PTFE powder was then addeduntil obtaining an uniform mixing. The obtained mixture wascharacterized as reported in Table 2.

EXAMPLE 4 (COMPARATIVE)

425 g of fluoroelastomer obtained in Example 3b were mixed in an openmixer with 75 g of PTFE MP 1600 by Du Pont by using the proceduredescribed in Example 3c. The mixture properties are reported in Table 2.

EXAMPLE 5

a) Preparation of the Semicrystalline Fluoropolymer

In a 50 l autoclave, equipped with a stirrer working at 245 rpm, afterevacuation, 32 l of demineralized water, 140 g of a paraffin withmelting point 52°-56° C. and 300 ml of a perfluoropolyoxyalkylenemicroemulsion were introduced: the latter was previously obtained bymixing:

-   -   65 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)F₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   65 ml of a 30% by volume NH₄OH aqueous solution;    -   130 ml of demineralized water;    -   40 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and the temperature wasprogressively increased up to 96° C. with a rate of 0.6° C./min for thewhole reaction duration. 370 mbar of C₂H₆ were fed into the autoclaveand the pressure was increased and maintained constant at 20 bar duringthe whole polymerization by feeding TFE.

2.5 g of ammonium persulphate (APS) as initiator agent were thenintroduced into the autoclave and subsequently by feeding, starting from10% of conversion, 0.54 g of APS every 10% of monomer conversion. After64 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex characteristics are reported in Table 3.

b) Preparation of the Fluoroelastomer

The fluoroelastomer latex was obtained as described in Example 1b,except that the amount of 1,6-diiodoperfluorohexane was of 30 g insteadof 26 g.

c) Mixing of the Latexes—Preparation of the Final Polymer

347 ml of the latex obtained in Example 5a are mixed with 1197 ml of theExample 5b latex. After mixing, the latex is coagulated with an aluminumsulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex) and driedat 80° C. in an air-circulating oven for 10 hours. 500 g of polymer,characterized as shown in Table 4, were obtained.

EXAMPLE 6

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 260 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   56.3 ml of a perfluoropolyoxyalkylene having an acid end group        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   56.3 ml of a 30% by volume NH₄OH aqueous solution;    -   112.7 ml of demineralized water;    -   34.7 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. 0.48 bar of ethane were fedinto the autoclave and the pressure was increased and maintainedconstant at 11 bar by continuously feeding TFE during thepolymerization.

6.5 g of ammonium persulphate (APS) were then introduced into theautoclave as initiator. After 15 minutes of reaction, the autoclave wascooled, degassed and discharged. The latex characteristics are reportedin Table 3. Subsequently 2368 ml (corresponding to 449.9 g of polymer)of the latex are introduced again in the 10 litre reactor to which 4132litres of demineralized water are added. The autoclave is then broughtto 90° C. and maintained for one hour at said temperature in order todecompose all the residual initiator agent.

Subsequently the temperature is increased to 80° C. and maintainedconstant for the whole duration of the polymerization. The followingmixture of monomers was then fed: perfluoromethylvinylether (PMVE) 60%by moles tetrafluoroethylene (TFE) 40% by molesso as to increase the pressure to 25 bar.

-   -   0.32 g of ammonium persulphate (ADS) as initiator agent;    -   22.3 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   4.28 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the        addition was carried out in 20 portions, each of 0.214 g,        starting from the polymerization beginning and for every 5%        increase in the monomer conversion,    -   were then introduced in the autoclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 45 minutes of reaction corresponding to 2550 g of elastomer, theautaoclave was cooled and the latex discharged. The latex is coagulatedwith an aluminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre oflatex) and dried at 80° C. in an air-circulating oven for 10 hours. Theobtained polymer was characterized as shown in Table 4.

EXAMPLE 7

a) Preparation of the Semicrystalline Fluoropolymer

The PTFE latex was obtained as described in Example 5a. The latexcharacteristics are reported in Table 3.

b) Preparation of the Fluoroelastomer

The fluoroelastomer latex was obtained as described in Example 5b. Thecharacteristics are reported in Table 3.

c) Mixing of the Latexes—Preparation of the Final Polymer

463 ml of the latex obtained in Example 7a are mixed with 1127 ml of theExample 7b latex. After mixing, the latex is coagulated with an aluminumsulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex) and driedat 80° C. in an air-circulating oven for 10 hours. The obtained polymerwas characterized as shown in Table 4.

EXAMPLE 8

The polymer obtained in Example 7c was crosslinked with bis-olefin offormula CH₂═CH— (CF₂)₆—O═CH₂, instead of TAIC. The compoundcharacteristics are reported in Table 4.

EXAMPLE 9

a) Preparation of the Semicrystalline Fluoropolymer

The PTFE latex was obtained as reported in Example 1a. The latexcharacteristics are reported in Table 5.

b) Preparation of the Fluoroelastomer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, 6.5 lof demineralized water and 26 g of ammonium perfluorooctanoate wereintroduced, after evacuation.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The following mixture ofmonomers was then fed: perfluoromethylvinylether (PMVE) 60% by molestetrafluoroethylene (TFE) 40% by molesso as to increase the pressure to 25 bar.

-   -   6.5 g of ammonium persulphate (APS) as initiator agent;    -   25 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   5 g of bis-olefin of formula CH₂═CH—(CF₂)_(n)—CH═CH₂; the        addition was carried out in 20 portions, each of 0.25 g,        starting from the polymerization beginning and for every 5%        increase in the monomer conversion,    -   were then introduced in the autoclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 500 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex properties are reported in Table 5.

c) Mixing of the Latexes—Preparation of the Final Polymer

551.5 ml of the latex obtained in Example 9a are mixed with 1393.5 ml ofthe Example 9b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 6, were obtained.

EXAMPLE 10

a) Preparation of the Semicrystalline Fluoropolymer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 65.1 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   14.1 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   14.1 ml of a 30% by volume NH₄OH aqueous solution;    -   28.2 ml of demineralized water;    -   8.7 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The autoclave waspressurized to the pressure of 0.56 bar with ethane and then to thepressure of 25 bar with a monomer mixture constituted by 10% by moles ofperfluoromethylvinylether (PMVE) and 90% by moles of tetrafluoroethylene(TFE)

1.3 g of ammonium persulphate (APS) as initiator agent were thenintroduced in the autoclave. During the reaction the pressure ismaintained at 25 bar by continuously feeding the following monomermixture: 3.5% by moles of PMVE and 96.5% of TFE.

After 60 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex characteristics are reported in Table 7.

b) Preparation of the Fluoroelastomer

In a 22 l autoclave, equipped with a stirrer working at 460 rpm, afterevacuation, 15 l of demineralized water and 154.5 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   33.46 ml of a perfluoropolyoxyalkylene, having an acid end        group, of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   33.46 ml of a 30% by volume NH₄OH aqueous solution;    -   66.93 ml of demineralized water;    -   20.65 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The following mixture ofmonomers was then fed: perfluoromethylvinylether (PMVE) 60% by molestetrafluoroethylene (TFE) 40% by molesso as to increase the pressure to 25 bar.

-   -   0.75 g of ammonium persulphate (APS) as initiator agent;    -   69.24 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   11.09 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the        addition was made in 20 portions, each of 0.554 g, starting from        the polymerization beginning and for every 5% increase in the        monomer conversion,    -   were then introduced in the autoclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 110 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex properties are reported in Table 7.

c) Mixing of the Latexes—Preparation of the Final Polymer

238 ml of the latex obtained in Example 10a are mixed with 1187 ml ofthe Example 10b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 8, were obtained.

EXAMPLE 11

In a 5 l autoclave, equipped with stirrer working at 630 rpm, afterevacuation, 3.5 l of demineralized water and 35 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   7.58 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   7.58 ml of a 30% by volume NH₄OH aqueous solution;    -   15.16 ml of demineralized water;    -   4.68 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The autoclave waspressurized to the pressure of 0.56 bar with ethane and then to thepressure of 25 bar with a monomer mixture formed by 10% by moles ofperfluoromethylvinylether (PMVE) and 90% by moles of tetrafluoroethylene(TFE).

In the autoclave 0.7 g of ammonium persulphate (APS) as initiator agentwere then introduced. During the reaction the pressure is maintained at25 bar by continuously feeding the following monomer mixture: 3.5% bymoles of PMVE and 96.5% of TFE.

After 10 minutes of reaction, the autoclave was cooled, degassed anddischarged. The latex characteristics are reported in Table 7.Subsequently 747 ml (corresponding to 225 g of polymer) of the latex areintroduced again in the 5 litres reactor to which 2.703 litres ofdemineralized water are added. The autoclave is then heated up to 90° C.and maintained for one hour at said temperature in order to decomposeall the residual initiator agent. Subsequently the temperature isbrought to 80° C. and maintained constant for the whole duration of thepolymerization. The following mixture of monomers was then fed:perfluoromethylvinylether (PMVE) 60% by moles tetrafluoroethylene (TFE)40% by molesso as to increase the pressure to 25 bar.

-   -   0.175 g of ammonium persulphate (APS) as initiator agent;    -   11.14 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   2.14 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the        addition was carried out in 20 portions, each of 0.107 g,        starting from the polymerization beginning and for every 5%        increase in the monomer conversion,    -   were then introduced in the autoclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 95 minutes of reaction corresponding to 1275 g of producedelastomer, the autoclave was cooled and the latex discharged.

The latex is coagulated with an aluminum sulphate solution (6 g ofAl₂(SO₄)₃ for each litre of latex) and dried at 80° C. in anair-circulating oven for 10 hours. The obtained polymer wascharacterized as shown in Table 8.

EXAMPLE 12 (COMPARATIVE)

a) Preparation of the Semicrystalline Fluoropolymer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 16.25 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   3.52 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   3.52 ml of a 30% by volume NH₄OH aqueous solution;    -   7.04 ml of demineralized water;    -   2.17 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The autoclave waspressurized to the pressure of 0.56 bar with ethane and then to thepressure of 25 bar with a monomer mixture formed by 10% by moles ofperfluoromethylvinylether (PMVE) and 90% by moles of tetrafluoroethylene(TFE).

In the autoclave 1.3 g of ammonium persulphate (APS) as initiator agentwere then introduced.

During the reaction the pressure is maintained at 25 bar by continuouslyfeeding the following monomer mixture: 3.5% by moles of PMVE and 96.5%of TFE.

After 65 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex characteristics are reported in Table 7.

b) Preparation of the Fluoroelastomer

The perfluoroelastomer latex was obtained as reported in Example 10b.The latex characteristics are reported in Table 7.

c) Mixing of the Latexes—Preparation of the Final Polymer

233.7 ml of the latex obtained in Example 12a are mixed with 1187 ml ofthe Example 12b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 8, were obtained.

EXAMPLE 13

a) Preparation of the Semicrystalline Fluoropolymer

The PTFE latex is obtained as reported in Example 9a. The latexproperties are reported in Table 9.

b) Preparation of the Fluoroelastomer

In a 10 l autoclave, equipped with stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 65.1 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   14.1 ml of a perfluoropolyoxyalkylene, having an acid end group        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   14.1 ml of a 30% by volume NH₄OH aqueous solution;    -   28.2 ml of demineralized water;    -   8.7 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The following mixture ofmonomers was then fed: vinylidene fluoride (VDF) 28% by molestetrafluoroethylene (TFE) 15% by moles hexafluoropropene (HFP) 57% bymolesso as to increase the pressure to 30 bar.

-   -   1.3 g of ammonium persulphate (APS) as initiator agent;    -   16.17 g of diiodomethane (CH₂I₂) as chain transfer agent fed        with the following procedure: 20% at the reaction beginning, 40%        when the conversion is equal to 20% and 40% when the conversion        is equal to 80%;    -   9 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the addition        was made in 20 portions, each of 0.45 g, starting from the        polymerization beginning and for every 5% increase in the        monomer conversion,    -   were then introduced in the autclave.

The 30 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by: vinylidene fluoride(VDF) 50% by moles tetrafluoroethylene (TFE) 25% by moleshexafluoropropene (HFP) 25% by moles

After 270 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex properties are reported in Table 9.

c) Mixing of the Latexes—Preparation of the Final Polymer

552 ml of the latex obtained in Example 14a are mixed with 1412 ml ofthe Example 14b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 10, were obtained.

EXAMPLE 14

a) Preparation of the Semicrystalline Fluoropolymer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 130 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   28.15 ml of a perfluoropolyoxyalkylene, having an acid end        group, of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   28.15 ml of a 30% by volume NH₄OH aqueous solution;    -   56.3 ml of demineralized water;    -   17.4 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The autoclave waspressurized to the pressure of 0.56 bar with ethane and then to thepressure of 20 bar by feeding a monomer mixture formed by 1.8% by molesof perfluoropropylvinylether (PPVE) and 98.2% by moles oftetrafluoroethylene (TFE).

In the autoclave 1.3 g of ammonium persulphate (APS) were thenintroduced as initiator. During the reaction the pressure is maintainedat 20 bar by continuously feeding the following monomer mixture: 1.8% ofPPVE and 98.2% of TFE.

After 18 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex characteristics are reported in Table 9.

b) Preparation of the Fluoroelastomer

In a 10 l autoclave, equipped with a stirrer working at 545 rpm, afterevacuation, 6.5 l of demineralized water and 65.1 ml of aperfluoropolyoxyalkylene microemulsion were introduced: the latter waspreviously obtained by mixing:

-   -   14.1 ml of a perfluoropolyoxyalkylene, having an acid end group,        of formula:        CF₂ClO(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₂COOH    -   wherein n/m=10, having average molecular weight of 600;    -   14.1 ml of a 30% by volume NH₄OH aqueous solution;    -   28.2 ml of demineralized water;    -   8.7 ml of Galden® D02 of formula:        CF₃O(CF₂—CF(CF₃)O)_(n)(CF₂O)_(m)CF₃    -   wherein n/m=20, having average molecular weight of 450.

The autoclave was then heated up to 80° C. and maintained at saidtemperature for the whole reaction duration. The following mixture ofmonomers was then fed: perfluoromethylvinylether (PMVE) 60% by molestetrafluoroethylene (TFE) 40% by molesso as to increase the pressure to 25 bar.

-   -   0.32 g of ammonium persulphate (APS) as initiator agent;    -   17 g of 1,6-diiodoperfluorohexane (C₆F₁₂I₂) as chain transfer        agent;    -   5 g of bis-olefin of formula CH₂═CH—(CF₂)₆—CH═CH₂; the addition        was effected in 20 portions, each of 0.25 g, starting from the        polymerization beginning and for every 5% increase in the        monomer conversion,    -   were then introduced in the autoclave.

The 25 bar pressure was maintained constant for the whole duration ofthe polymerization by feeding a mixture formed by:perfluoromethylvinylether (PMVE) 40% by moles tetrafluoroethylene (TFE)60% by moles

After 80 minutes of reaction, the autoclave was cooled and the latexdischarged. The latex properties are reported in Table 9.

c) Mixing of the Latexes—Preparation of the Final Polymer

528 ml of the latex obtained in Example 15a are mixed with 1218 ml ofthe Example 15b latex. After mixing, the latex is coagulated with analuminum sulphate solution (6 g of Al₂(SO₄)₃ for each litre of latex)and dried at 80° C. in an air-circulating oven for 10 hours. 500 g ofpolymer, characterized as shown in Table 10, were obtained. TABLE 1Latex con- Particle MFI⁽¹⁾ Mooney centration diameter ASTM (1 +10)^(121° C.) (g/l) (nm) D 1238 ASTM D 1646 Example 1a 118 12 82.7 —Example 1b 280 54 — 27 Example 2a 175 197 0.2 — (comp.) Example 2b 28054 — 27 (comp.)⁽¹⁾MFI has been determined at 380° C. with 3 Kg

TABLE 2 EXAMPLE Ex. 2c Ex. 3c Ex. 4 Ex. 1c comp. comp. comp. % by weightof plastomer 15 15 15 15 ML(1 + 10)^(121° C.) (ASTM D 1646) 58 nd 27 —Formulation: Elastomer (phr) 100 100 100 100 TAIC ″ 1.5 1.5 1.5 1.5Luperco ″ 2 2 2 2 ZnO ″ 5 5 5 5 ODR (177° C., 12′arc 3°) (ASTMD2084-81): ML Lbf. in. 11 nd 17 13 MH ″ 118 nd 115 140 Ts2 sec 45 nd 4551 T′90 ″ 99 nd 90 109 Molding in press at 180° C. for 10 min: Sheetsurface smooth nd rough rough Mechanical properties after post cure at200° C. for 1 hour (ASTM D 412-83): M100 Mpa 4.9 nd 10.1 6.3 C.R. ″ 19.3nd 18.5 18.7 A.R. % 174 nd 145 174 ShA Hardness points 69 nd 85 76Compression set on O-ring (ASTM D 395): 200° C. for 70 hours (%) 29 nd40 broken 230° C. for 70 hours (%) 47 nd broken —

TABLE 3 Latex con- Particle MFI⁽¹⁾ Mooney centration diameter ASTM (1 +10)^(121° C.) (g/l) (nm) D 1238 ASTM D 1646 Example 5a 216 90 2 —Example 5b 355 60 — 20 Example 6 190 50 54.1 — Example 7a 216 90 2 —Example 7b 355 60 — 18⁽¹⁾MFI has been determined at 380° C. with 3 Kg

TABLE 4 EXAMPLE Ex. 5c Ex. 6 Ex. 7c Ex. 8 % by weight of plastomer 15 1520 20 ML(1 + 10)^(121° C.) (ASTM D 1646) 35 39 41 35 Formulation:Elastomer (phr) 100 100 100 100 TAIC ″ 1.5 1.5 1.5 — BO⁽²⁾ — — — 4Luperco ″ 2 2 2 4 ZnO ″ 5 5 5 5 ODR (177° C., 12′arc 3°) (ASTMD2084-81): ML Lbf. in. 8 6 12 4 MH ″ 131 108 133 77 Ts2 sec 45 52 60 78T′90 ″ 285 138 123 330 Molding in press at 180° C. for 10 min: Sheetsurface smooth smooth smooth smooth Mechanical properties after postcure at 200° C. for 1 h (ASTM D 412-83): M100 Mpa 5.6 4.5 7.9 10.1 C.R.″ 16.4 16.9 18.4 18.5 A.R. % 164 190 154 145 ShA Hardness points 73 7278 85 Compression set on O-ring (ASTM D 395): 200° C. for 70 hours (%)28 49 33 43⁽²⁾Bisolefin of formula CH₂═CH—(CF₂)₆—CH═CH₂

TABLE 5 Latex con- Particle MFI Mooney centration diameter ASTM (1 +10)^(121° C.) (g/l) (nm) D 1238 ASTM D 1646 Example 9a 136 12 82.7⁽¹⁾ —Example 9b 305 163 — 38⁽¹⁾MFI has been determined at 380° C. with 3 Kg

TABLE 6 EXAMPLE Ex. 9c % by weight of plastomer 15 ML(1 + 10)^(121° C.)(ASTM D 1646) 48 Formulation: Elastomer (phr) 100 TAIC ″ 1.5 Luperco ″ 2ZnO ″ 5 ODR (177° C., 12′arc 3°) (ASTM D2084-81): ML Lbf. in. 11 MH ″ 95Ts2 sec 48 T′90 ″ 103 Molding in press at 180° C. for 10 min: Sheetsurface smooth Mechanical properties after post cure at 200° C. for 1hour (ASTM D 412-83): M100 Mpa 6.3 C.R. ″ 22.2 A.R. % 184 ShA hardnesspoints 73 Compression set on O-ring (ASTM D 395): 200° C. for 70 hours(%) 47

TABLE 7 Latex con- Particle MFI Mooney centration diameter ASTM (1 +10)^(121° C.) (g/l) (nm) D 1238 ASTM D 1646 Example 10a 315 60 295⁽¹⁾ —Example 10b 358 54 — 15 Example 11 301 26 216⁽²⁾ — Ex. 12a comp. 321 103245⁽¹⁾ — Ex. 12b comp. 358 54 — 15⁽¹⁾MFI has been measured at 372° C. with 5 Kg⁽²⁾MFI has been measured at 372° C. with 10 Kg

TABLE 8 EXAMPLE Ex. 12c Ex. 10c Ex. 11 comp. % by weight of plastomer 1515 15 ML(1 + 10)^(121° C.) (ASTM D 1646) 27 55 28 Formulation: Elastomer(phr) 100 100 100 TAIC ″ 1.5 1.5 1.5 Luperco ″ 2 2 2 ZnO ″ 5 5 5 ODR(177° C., 12′arc 3°) (ASTM D2084-81): ML Lbf. in. 5 20 5 MH ″ 129 134 83Ts2 sec 54 46 54 T′90 ″ 114 97 99 Molding in press at 180° C. for 10min: Sheet surface smooth smooth rough Mechanical properties after postcure at 200° C. for 1 hour (ASTM D 412-83): M100 Mpa 5.7 7.1 6.6 C.R. ″16.4 19.0 18.4 A.R. % 175 183 177 ShA hardness points 70 79 73Compression set on O-ring (ASTM D 395): 200° C. for 70 hours (%) 29 47 —

TABLE 9 Latex con- Particle MFI Mooney centration diameter ASTM (1 +10)^(121° C.) (g/l) (nm) D 1238 ASTM D 1646 Example 13a 136 12 29.1⁽¹⁾ —Example 13b 301 72 — 51 Example 14a 142 60 80⁽²⁾ — Example 14b 349 54 —68⁽¹⁾MFI has been measured at 380° C. with 3 Kg⁽²⁾MFI has been measured at 372° C. with 5 Kg

TABLE 10 EXAMPLE Ex. 13c Ex. 14c % by weight of plastomer 15 15 ML(1 +10)^(121° C.) (ASTM D 1646) 73 73 Formulation: Elastomer (phr) 100 100TAIC ″ 3 1.5 Luperco ″ 4 2 ZnO ″ 5 5 ODR (177° C., 12′arc 3°) (ASTMD2084-81): ML Lbf. in. 12 30 MH ″ 96 130 Ts2 sec 55 55 T′90 ″ 115 118Molding in press at 180° C. for 10 min: Sheete surface smooth smoothMechanical properties after post cure at 200° C. for 1 hour (ASTM D412-83): M100 Mpa 4 6.2 C.R. ″ 16.5 15.0 A.R. % 344 164 ShA hardnesspoints 65 73 Compression set on O-ring (ASTM D 395): 200° C. for 70hours (%) — 32

1. Cured fluoropolymer compositions comprising a fluoroelastomer and asemicrystalline fluoropolymer latex formed by tetrafluoroethylene (TFE)homopolymers, or TFE copolymers with one or more monomers containing atleast one unsaturation of ethylene type in amounts ranging from 0.01% to10% by moles, obtainable by mixing the semicrystalline fluoropolymerlatex with the fluoroelastomer, subsequent coagulation and drying. 2.Cured fluoropolymer compositions according to claim 1 obtainable bypolymerizing in a first step the semicrystalline fluoropolymer and in asecond step the fluoroelastomer.
 3. Cured fluoropolymer compositionsaccording to claim 1 wherein the semicrystalline fluoropolymer amountinside the fluoroelastomer matrix is in the range 2-40% by weight of thetotal of the polymeric mixture.
 4. Cured fluoropolymer compositionsaccording to claim 3 wherein the semicrystalline fluoropolymer amountinside the fluoroelastomer matrix is in the range 5-30% by weight of thetotal of the polymeric mixture.
 5. Cured fluoropolymer compositionsaccording to claim 1 wherein the semicrystalline polymer is based onPTFE modified with comonomers with ethylene unsaturation both ofhydrogenated and fluorinated type.
 6. Cured fluoropolymer compositionsaccording to claim 5 wherein the hydrogenated comonomers are selectedfrom the group consisting of ethylene, propylene, methylmethacrylate,methacrylic acid, butylacrylate, hydroxyethylhexylacrylate, and styrene.7. Cured fluoropolymer compositions according to claim 5 wherein thefluorinated comonomers are selected from the group consisting of:perfluoroolefins C₃-C₈; hydrogenated fluoroolefins C₂-C₈; chloro- and/orbromo- and/or iodo-fluoroolefins C₂-C₈; (per)fluoroalkylvinylethers(PAVE CF₂═CFOR_(f), wherein R_(f) is a (per)fluoroalkyl C₁-C₆;(per)fluoro-oxyalkyvinylethers CF₂═CFOX, wherein X is a alkyl C₁-C₁₂, oran oxyalkyl C₁-C₁₂, or a (per)fluoro-oxyalkyl C₁-C₁₂ having one or moreether groups; fluorodioxoles.
 8. Cured fluoropolymer compositionsaccording to claim 5 wherein the fluorinated comonomers are selectedfrom the group consisting of perfluoromethyl-, ethyl-, propylvinyletherand perfluorodioxoles.
 9. Cured fluoropolymer compositions according toclaim 1 wherein the fluoroelastomer is selected from the followingclasses: (1) vinylidene fluoride (VDF)-based copolymers, wherein VDF iscopolymerized with at least one comonomer selected from the groupconsisting of: perfluoroolefins C₂-C₈, chloro- and/or bromo- and/oriodofluoroolefins C₂-C₈, (per)fluoroalkyl-vinylethers (PAVE)CF₂═CFOR_(f), wherein R_(f) is a (per)fluoroalkyl C₁-C₆,perfluoro-oxyalkylvinylethers CF₂═CFOX, wherein X is aperfluoro-oxyalkyl C₁-C₁₂ having one or more ether groups, nonfluorinated olefins (Ol) C₂-C₈; (2) tetrafluoroethylene (TFE)-basedcopolymers, wherein TFE is copolymerized with at least one comonomerselected from the group consisting of (per)fluoroalkyvinylethers (PAVE)CF₂═CFOR_(f), wherein R_(f) is as above defined;perfluoro-oxyalkyvinylethers CF₂═CFOX, wherein X is as above defined;fluoroolefins C₂-C₈ containing hydrogen and/or chlorine and/or bromineand/or iodine atoms; non fluorinated olefins (Ol) C₂-C₈.
 10. Curedfluoropolymer compositions according to claim 9 wherein thefluorelastomer is selected from the following compositions expressed bymoles: (a) vinylidene fluoride (VDF) 45-85%, hexafluoropropene (HFP)15-45% tetrafluoroethylene (TFE) 0-30%; (b) vinylidene fluoride (VDF)50-80%, perfluoroalkylvinylether (PAVE) 5-50%, tetrafluoroethylene (TFE)0-20%; (c) vinylidene fluoride (VDF) 20-30%, non fluorinated olefins(Ol) C₂-C₈ 10-30%, hexafluoropropene (HFP) and/orperfluoroalkylvinylether (PAVE) 18-27%, tetrafluoroethylene (TFE)10-30%; (d) tetrafluoroethylene (TFE) 50-80%, perfluoroalkylvinylether(PAVE) 20-50%; (e) tetrafluoroethylene (TFE) 45-65%, non fluorinatedolefins (Ol) C₂-C₈ 20-55%, vinylidene fluoride 0-30% (f)tetrafluoroethylene (TFE) 32-60%, non fluorinated olefins (Ol) C₂-C₈10-40%, perfluoroalkylvinylether (PAVE) 20-40%; (g) tetrafluoroethylene(TFE) 33-75%, perfluoroalkylvinylether (PAVE) 15-45%, vinylidenefluoride (VDF) 5-30%.
 11. Cured fluoropolymer compositions according toclaim 1 wherein the fluoroelastomer comprises also monomer unitsderiving from a bis-olefin having the formula:

wherein R₁, R₂, R₃, R₄, R₅, R₆, equal to or different from each other,are H or alkyl C₁-C₅; Z is a linear or branched, alkylene orcycloalkylene C₁-C₁₈ radical, optionally containing oxygen tomsoptionally at least partially fluorinated, or a(per)fluoropolyoxyalkylene radical.
 12. Cured fluoropolymer compositionsaccording to claim 11 wherein the unit amount in the chain deriving fromthe bis-olefin is in the range 0.01-1.0% by moles of the other monomerunits forming the fluoroelastomer base structure.
 13. Curedfluoropolymer compositions according to claim 1 wherein thefluoroelastomers are cured by peroxidic route.
 14. Cured fluoropolymercompositions according to claim 1 wherein when the fluoroelastomerscontain cyano groups they are cured by tin organic compounds and/ordiaromatic aminic compounds.
 15. Cured fluoropolymer compositionsaccording to claim 1 wherein the fluoroelastomers are cured by tinorganic compounds and/or diaromatic aminic compounds and optionally byperoxidic route if in the polymeric chain iodine and/or bromine atomsare present.
 16. Cured fluoropolymer compositions according to claim 1wherein the one or more monomers containing at least one unsaturation ofethylene type are present in amounts ranging from 0.5% to 5% by moles.17. Cured fluoropolymer compositions according to claim 7 wherein theperfluoroolefins C₃-C₈ are selected from the group consisting ofhexafluoropropene (HFP) and hexafluoroisobutene.
 18. Cured fluoropolymercompositions according to claim 7 wherein the hydrogenated fluoroolefinsC₂-C₈ are selected from the group consisting of vinyl fluoride (VF),vinylidene fluoride (VDF), trifluoroethylene and perfluoroalkylethyleneCH₂═CH—R_(f), wherein R_(f) is a perfluoroalkyl C₁-C₆.
 19. Curedfluoropolymer compositions according to claim 7 wherein thechlorofluoroolefin C₂-C₈ is chlorotrifluoroethylene (CTFE).
 20. Curedfluoropolymer compositions according to claim 7 wherein the(per)fluoroalkylvinyl-ethers (PAVE) (CF₃═CF)R_(f)) are selected from thegroup consisting of CF₃, C₂F₅ and C₃F₇.
 21. Cured fluoropolymercompositions according to claim 7 wherein the (per)fluorooxyalkyl C₁-C₁₂having one or more ether groups is perfluoro-2-propoxy-propyl.
 22. Curedfluoropolymer compositions according to claim 9 wherein theperfluoroolefin C₂-C₈ is selected from the group consisting oftetrafluoroethylene (TFE) and hexafluoropropene (HFP).
 23. Curedfluoropolymer compositions according to claim 9 wherein the chloro-and/or bromo-fluoro-olefins C₂-C₈ are selected from the group consistingof chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene.
 24. Curedfluoropolymer compositions according to claim 9 wherein the(per)fluoroalkyl-vinylethers (PAVE) CF₂—CFOR_(f) are selected from thegroup consisting of trifluoromethyl, bromodifluoromethyl andpentafluoropropyl.
 25. Cured fluoropolymer compositions according toclaim 9 wherein the perfluorooxyalkylvinylether CF₂═CFOX isperfluoro-2-propoxy-propyl.
 26. Cured fluoropolymer compositionsaccording to claim 9 wherein the nonfluorinated olefins (Ol) C₂-C₈ areselected from the group consisting of ethylene and propylene.
 27. Asealing manufactured article comprising the cured fluoropolymercompositions according to claim
 1. 28. The sealing manufactured articleaccording to claim 27, wherein the sealing manufactured article is anO-ring.
 29. Cured fluoropolymers comprising a fluoroelastomer matrixincorporating therein particles of a semicrystalline fluoropolymer latexformed by tetrafluoroethylene (TFE) homopolymers, or TFE copolymers withone or more monomers containing at least one unsaturation of ethylenetype in amounts ranging from 0.01% to 10% by moles.
 30. Curedfluoropolymers according to claim 29 obtainable by mixing thesemicrystalline fluoropolymer latex with the fluoroelastomer latex andsubsequent coagulation.
 31. Cured fluoropolymers according to claim 29obtainable by polymerizing in a first step the semicrystallinefluoropolymer and in a second step the fluoroelastomer.
 32. Curedfluoropolymers according to claim 29 wherein the semicrystallinefluoropolymer amount inside the fluoroelastomer matrix is in the range2-40% by weight of the total of the polymeric mixture.
 33. Curedfluoropolymers according to claim 32 wherein the semicrystallinefluoropolymer amount inside the fluoroelastomer matrix is in the range5-30% by weight of the total of the polymeric mixture.
 34. Curedfluoropolymers according to claim 29 wherein the semicrystalline polymeris based on PTFE modified with comonomers with ethylene unsaturationboth of hydrogenated and fluorinated type.
 35. Cured fluoropolymersaccording to claim 34 wherein the hydrogenated comonomers are selectedfrom the group consisting of ethylene, propylene, methylmethacrylate,methacrylic acid, butylacrylate, hydroxyethylhexylacrylate, and styrene.36. Cured fluoropolymers according to claim 34 wherein the fluorinatedcomonomers are selected from the group consisting of perfluoroolefinsC₃-C₈; hydrogenated fluoroolefins C₂-C₈; chloro- and/or bromo- and/oriodo-fluoroolefins C₂-C₈; (per)fluoroalkylvinyl ethers (PAVE)CF₂═CFOR_(f), wherein R_(f) is a (per)fluoroalkyl C₁-C₆;(per)fluoro-oxyalkyvinylethers CF₂═CFOX, wherein X is an alkyl C₁-C₁₂,or an oxyalkyl C₁-C₁₂, or a (per)fluoro-oxyalkyl C₁-C₁₂ having one ormore ether groups; fluorodioxoles.
 37. Cured fluoropolymers according toclaim 34 wherein the fluorinated comonomers are selected from the groupconsisting of perfluoromethyl-, ethyl-, propyl-vinylether andperfluorodioxoles.
 38. Cured fluoropolymers according to claim 29wherein the fluoroelastomer is selected from the following classes: (1)vinylidene fluoride (VDF)-based copolymers, wherein VDF is copolymerizedwith at least one comonomer selected from the group consisting of:perfluoroolefins C₂-C₈, chloro- and/or bromo- and/or iodofluoroolefinsC₂-C₈, (per)fluoroalkyl-vinylethers (PAVE) CF₂═CFOR_(f), wherein R_(f)is a (per)fluoroalkyl C₁-C₆, perfluoro-oxyalkyvinylethers CF₂═CFOX,wherein X is a perfluoro-oxyalkyl C₁-C₁₂ having one or more ethergroups, non fluorinated olefins (Ol) C₂-C₈; (2) Tetrafluoroethylene(TFE)-based copolymers, wherein TFE is copolymerized with at least onecomonomer selected from the group consisting of(per)fluoroalkylvinylethers (PAVE) CF₂═CFOR_(f), wherein R_(f) is asabove defined; perfluoro-oxyalkyvinylethers CF₂═CFOX, wherein X is asabove defined; fluoroolefins C₂-C₈ containing hydrogen and/or chlorineand/or bromine and/or iodine atoms; non fluorinated olefins (Ol) C₂-C₈;perfluorovinylethers containing hydrocyanic groups.
 39. Curedfluoropolymers according to claim 38 wherein the fluoroelastomers isselected from the following compositions expressed by moles: (a)vinylidene fluoride (VDF) 45-85%, hexafluoropropene (HFP) 15-45%tetrafluoroethylene (TFE) 0-30%; (b) vinylidene fluoride (VDF) 50-80%,perfluoroalkylvinylether (PAVE) 5-50%, tetrafluoroethylene (TFE) 0-20%;(c) vinylidene fluoride (VDF) 20-30%, non fluorinated olefins (Ol) C₂-C₈10-30%, hexafluoropropene (HFP) and/or perfluoroalkylvinylether (PAVE)18-27%, tetrafluoroethylene (TFE) 10-30); (d) tetrafluoroethylene (TFE)50-80%, perfluoroalkylvinylether (PAVE) 20-50%; (e) tetrafluoroethylene(TFE) 45-65%, non fluorinated olefins (Ol) C₂-C₈ 20-55%, vinylidenefluoride 0-30%; (f) tetrafluoroethylene (TFE) 32-60% by moles, nonfluorinated olefins (Ol) C₂-C₈ 10-40%, perfluoroalkylvinylether (PAVE)20-40%; (g) tetrafluoroethylene (TFE) 33-75%, perfluoroalkylvinylether(PAVE) 15-45%, vinylidene fluoride (VDF) 5-30%.
 40. Cured fluoropolymersaccording to claim 29 wherein the fluoroelastomer comprises also monomerunits deriving from a bis-olefin having the formula:

wherein R₁, R₂, R₃, R₄, R₅, R₆, equal to or different from each other,are H or alkyl C₁-C₅; Z is a linear or branched, alkylene orcycloalkylene C₁-C₁₈ radical, optionally containing oxygen atomsoptionally at least partially fluorinated, or a(per)fluoropolyoxyalkylene radical.
 41. Cured fluoropolymers accordingto claim 40 wherein the unit amount in the chain deriving from thebis-olefin is in the range 0.01-1.0% by moles of the other monomer unitsforming the fluoroelastomer base structure.
 42. Cured fluoropolymersaccording to claim 29 wherein the fluoroelastomers are cured byperoxidic route.
 43. Cured fluoropolymers according to claim 29 whereinwhen the fluoroelastomers contain cyano groups they are cured by tinorganic compounds and/or di-aromatic aminic compounds.
 44. Curedfluoropolymers according to claim 29 wherein the fluoroelastomers arecured by tin organic compounds and/or diaromatic aminic compounds andoptionally by peroxidic route if in the polymeric chain iodine and/orbromine atoms are present.
 45. Cured fluoropolymers according to claim29 wherein the one or more monomers containing at least one unsaturationof ethylene type are present in amounts ranging from 0.5% to 5% bymoles.
 46. Cured fluoropolymers according to claim 36 wherein theperfluoroolefins C₃-C₈ are selected from the group consisting ofhexafluoropropene (HFP) and hexafluoroisobutene.
 47. Curedfluoropolymers according to claim 36 wherein the hydrogenatedfluoroolefins C₂-C₈ are selected from the group consisting of vinylfluoride (VF), vinylidene fluoride (VDF), trifluoroethylene andperfluoroalkylethylene CH₂═CH—R_(f), wherein R_(f) is a perfluoroalkylC₁-C₆.
 48. Cured fluoropolymers according to claim 36 wherein thechloro-fluoroolefin C₂-C₈ is chlorotrifluoroethylene (CTFE).
 49. Curedfluoropolymers according to claim 36 wherein the(per)fluoroalkylvinylethers (PAVE) (CF₂═CFOR_(f)) are selected from thegroup consisting of CF₃, C₂F₅ and C₃F₇.
 50. Cured fluoropolymersaccording to claim 36 wherein the (per)fluoro-oxyalkyl C₁-C₁₂ having oneor more ether groups is perfluoro-2-propoxy-propyl.
 51. Curedfluoropolymers according to claim 38 wherein the perfluoroolefin C₂-C₈is selected from the group consisting of tetrafluoroethylene (TFE) andhexafluoropropene (HFP).
 52. Cured fluoropolymers according to claim 38wherein the chloro- and/or bromofluoro-olefins C₂-C₈ are selected fromthe group consisting of chlorotrifluoroethylene (CTFE) andbromotrifluoroethylene.
 53. Cured fluoropolymers according to claim 38wherein the (per)fluoroalkylvinylethers (PAVE) CF₂═CFOR_(f) are selectedfrom the group consisting of trifluoromethyl, bromodifluoromethyl andpentafluoropropyl.
 54. Cured fluoropolymers according to claim 38wherein the perfluorooxyalkylvinylether CF₂═CFOX isperfluoro-2-propoxy-propyl.
 55. Cured fluoropolymers according to claim38 wherein the nonfluorinated olefins (01) C₂-C₈ are selected from thegroup consisting of ethylene and propylene.
 56. A sealing manufacturedarticle comprising the cured fluorelastomer of anyone of claims 28-54.57. The sealing article according to claim 56, wherein the sealingarticle manufactured article is an O-ring.